Pickup reading anomaly

victorludorum · October 2020

Last year i bought a replica XII pickup, and when it arrived it read 5.5ish on my multimeter, which was much less that the 7k that I'd asked for. I agreed a partial refund with the guy who was very good about it it and I put the pickup to one side with the intention of selling it down the line. I've now got round to putting it up for sale and have just re-done the reading for the ad and it's coming out at 6.89!!! I remember checking the reading a few times when i got it, to be absolutely sure that there was a problem before contacting the seller, so it isn't just a case of one dodgy reading. How can something like this happen? I haven't changed the battery in the meter and it's always worked and given readings that I've expected for many components, so I don't think it can be that. Could temperature changes be playing a part?

phil_b · October 2020

if you were holding the meter probes in your fingers you can add your body resistance into the circuit giving a false reading

Funkfingers · October 2020

The meter battery is the most obvious culprit. OTOH, the resistance reading from the coil(s) can vary with temperature.

In the meantime, you might want to contact the pickup builder, explain the situation and refund the refund.

victorludorum · October 2020

Funkfingers said:

The meter battery is the most obvious culprit. OTOH, the resistance reading from the coil(s) can vary with temperature.

In the meantime, you might want to contact the pickup builder, explain the situation and refund the refund.

I'm surprised that a difference as large as that could be related to temperature. I bought it in September last year, so the temp will be roughly the same.

I've already sent the guy a message and will do the necessary.

Funkfingers · October 2020

victorludorum said:
I'm surprised that a difference as large as that could be related to temperature.

So am I.

PonchoGreg · October 2020

victorludorum said:

I'm surprised that a difference as large as that could be related to temperature.

That's what she said.

Seriously though - that's very odd, especially if the battery isn't a factor. I've had a few variances in readings a few months apart for a pickup, but never to the magnitude of ~20%.

Good on you for getting back in touch with the seller though, a lot of people wouldn't.

Danny1969 · October 2020

You can reduce the reading if you were holding it in such a way your bodies resistance was in parallel with the coil. That will give a lower reading.

DC resistance and impedance aren't the sane thing. Did you have it on DC OHMs's or an impedance setting ... basically an impedance reading is affected by the construction of a conductor, like a speaker coil or a pickup coil or an inductor for example.

It's not temperature ... you need to go very very cold for the resistance of a piece of wire to change.

victorludorum · October 2020

Danny1969 said:

You can reduce the reading if you were holding it in such a way your bodies resistance was in parallel with the coil. That will give a lower reading.

DC resistance and impedance aren't the sane thing. Did you have it on DC OHMs's or an impedance setting ... basically an impedance reading is affected by the construction of a conductor, like a speaker coil or a pickup coil or an inductor for example.

It's not temperature ... you need to go very very cold for the resistance of a piece of wire to change.

I think this is probably it. I have a basic multimeter and always use the resistance setting, as I think that's all it has.

Sassafras · October 2020

I don't understand the importance people place on a pickup's resistance.
I don't think it's a reliable indication of output.

victorludorum · October 2020

Sassafras said:

I don't understand the importance people place on a pickup's resistance.
I don't think it's a reliable indication of output.

I wanted it to balance well with the bridge pickup, so it seemed like the obvious reading to use.

ICBM · October 2020

victorludorum said:

Sassafras said:

I don't understand the importance people place on a pickup's resistance.
I don't think it's a reliable indication of output.

I wanted it to balance well with the bridge pickup, so it seemed like the obvious reading to use.

It's only a useful guide when everything else is identical, because it gives an approximation of the difference in the number of turns. And even then, not quite - the resistance rises faster than the number of turns as the length of wire in each turn becomes longer as the coil gets fatter, although that's probably irrelevant over the sort of range here.

I can't explain such a big discrepancy as a reading of 5.5K from a 7K pickup though. Temperature shouldn't make that much difference, and I think that if the multimeter battery was on the way out it would stop working at all long before it gave that big an error.

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Pickup reading anomaly

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